一、Extract Class（提炼类）
动机（Motivation）
一个class应该是一个清楚的抽象（abstract），处理一些明确的责任。但在实际工作中，class会不断成长扩展。这个class会变得过份复杂，很快，class就会变成一团乱麻。
示例
public class Person { private string _name; private string _officeAreaCode; private string _officeNumber; public string Name { get { return _name; } set { _name = value; } } public string OfficeAreaCode { get { return _officeAreaCode; } set { _officeAreaCode = value; } } public string OfficeNumber { get { return _officeNumber; } set { _officeNumber = value; } } public string TelephoneNumber { get { return "(" + _officeAreaCode + ")" + _officeNumber; } } } 改为
public class Person { private string _name; private Telephone _telephoneNumber; public Telephone TelephoneNumber { get { return _telephoneNumber; } set { _telephoneNumber = value; } } public string Name { get { return _name; } set { _name = value; } } public string TemphoneNumber { get { return _telephoneNumber.TelephoneNumber; } } } public class Telephone { private string _officeAreaCode; private string _officeNumber; public string OfficeAreaCode { get { return _officeAreaCode; } set { _officeAreaCode = value; } } public string OfficeNumber { get { return _officeNumber; } set { _officeNumber = value; } } public string TelephoneNumber { get { return "(" + _officeAreaCode + ")" + _officeNumber; } } } 二、Inline Class（将类内联化）
动机（Motivation）
一个class不再承担足够责任、不再有单独存在的理由，将class的所有特性搬移到另一个class中，然后移除原class。
示例
public class User { private int _ID; private string _name; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } } public class UserInfo { private int _ID; private string _Age; public string ID { get { return _ID; } set { _ID = value; } } public string Age { get { return _Age; } set { _Age = value; } } } 改为
public class User { private int _ID; private string _name; private string _Age; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } public string Age { get { return _Age; } set { _Age = value; } } } 三、Hide Delegate（隐藏[委托关系]）
动机（Motivation）
[封装]即使不是对象的最关键特征，也是最关键特征之一。[封装]意味每个对象都应该尽可能少了解系统的其它部分。如此一来，一旦发生变化，需要了解这变化的对象就会比较少，这会使谈化比较容易进行。
示例
public class User { private int _ID; private string _name; private Department _depart; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } public Department Depart { get { return _depart; } set { _depart = value; } } } public class Department { private string _departName; private User _manager; public string DepartName { get { return _departName; } set { _departName = value; } } public User Manager { get { return _manager; } set { _manager = value; } } } 改为
public class User { private int _ID; private string _name; private Department _depart; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } public Department Depart { get { return _depart; } set { _depart = value; } } public string DepartmentManager { get { return _depart.Manager; } } } public class Department { private string _departName; private User _manager; public string DepartName { get { return _departName; } set { _departName = value; } } public User Manager { get { return _manager; } set { _manager = value; } } } 这样取部门管理者就更直接，更方便，适合于少量使用。
但如果有大量的方法都用到了DepartmentManager里，我们就要去掉中间人了。
四、Remove Middle Man（移除中间人）
动机（Motivation）
大量重复的代码是万恶之源。这些重复性代码应该抽出来放进同一个函数中。
示例
public class User { private int _ID; private string _name; private Department _depart; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } public Department Depart { get { return _depart; } set { _depart = value; } } public string DepartmentManager { get { return _depart.Manager; } } } public class Department { private string _departName; private User _manager; public string DepartName { get { return _departName; } set { _departName = value; } } public User Manager { get { return _manager; } set { _manager = value; } } } 改为
public class User { private int _ID; private string _name; private Department _depart; public int ID { get { return _ID; } set { _ID = value; } } public string Name { get { return _name; } set { _name = value; } } public Department Depart { get { return _depart; } set { _depart = value; } } } public class Department { private string _departName; private User _manager; public string DepartName { get { return _departName; } set { _departName = value; } } public User Manager { get { return _manager; } set { _manager = value; } } } 在调用时就直接Depart.Manager来取得它的值.